Polymers and copolymers of, and surgical devices made from lactide and/or glycolide and/or related compounds are well-known. See, e.g., U.S. Pat. Nos. 2,668,162, 2,683,136, 2,703,316, 2,758,987, 3,225,766, 3,268,486, 3,268,487, 3,297,033, 3,422,181, 3,442,871, 3,463,158, 3,468,853, 3,531,561, 3,565,869, 3,597,449, 3,620,218, 3,626,948, 3,636,956, 3,736,646, 3,739,773, 3,772,420, 3,733,919, 3,781,349, 3,784,585, 3,792,010, 3,797,499, 3,839,297, 3,846,382, 3,867,190, 3,987,937, 3,878,284, 3,896,802, 3,902,497, 3,937,223, 3,982,543, 4,033,938, 4,045,418, 4,057,537, 4,060,089, 4,137,921, 4,157,437, 4,243,775, 4,246,904, 4,273,920, 4,275,813, 4,279,249, 4,300,565, and 4,744,365, U.K. Pat. or Appln. Nos. 779,291, 1,332,505, 1,414,600 and 2,102,827, D. K. Gilding et al., "Biodegradable polymers for use in surgery-polyglycolic/poly (lactic acid) homo- and copolymers: 1, "Polymer, Volume 20, pages 1459-1464 (1979), and D. F. Williams (ed.) Biocompatibility Of Clinical Implant Materials, Volume II, chapter 9: "Biodegradable Polymers" (1981).
Surgical devices prepared from copolymers containing lactide or glycolide and trimethylene carbonate have been described.
U.S. Pat. No. 4,429,080 describes glycolide end blocks and glycolide trimethylene carbonate random copolymer middle blocks. The block copolymers described in the '080 patent contain no 1,4 dioxane-2-one.
As another example, U.S. Pat. No. 5,066,772 describes random copolymers of lactide and trimethylene carbonate and triblock copolymers having lactide end blocks and lactide-trimethylene carbonate random copolymer center blocks. The block copolymers of the '772 patent do not include a block which has predominantly glycolic acid ester linkages.
Block copolymers described in U.S. Pat. No. 5,145,945 do not include a block having random copolymers of trimethylene carbonate and dioxanone nor do they include a block which is predominantly glycolide. In addition, see U.S. Pat. Nos. 4,243,775; 4,300,565; 4,705,820; 4,891,263; 4,916,193; 4,902,203; 5,037,950, and 5,252,701.
As described above bioabsorbable sutures are known in the art. However, in the manufacture of sutures an important characteristic of a suture is the amount of effort typically required to straighten the suture upon its removal from the package in order to ready the suture for use. This effort appears to be related to the "strain energy" of the suture, i.e., the integration of the stress-strain curve for the suture measured in kilogram-mm, and is equivalent to the work expended in elongating the monofilament by a specified percentage of its original length. As the strain energy of a given size of suture decreases so, too, does the amount of effort required to straighten the suture prior to use. A decrease in strain energy also appears to relate to the perceived flexibility of the suture, another important characteristic.
Therefore, it would be advantageous to provide a bioabsorbable suture which exhibits good flexibility and handling characteristics while maintaining other desired characteristics, such as knot strength, knot retention and desired absorption characteristics.